In a wireless communication system, various wireless access schemes such as a multi-tier network and a heterogeneous network can interwork with each other. Such a wireless communication system includes relay configured to relay wireless communication between a donor base-station and a user equipment (UE). Generally, a fixed relay constituting a small cell at a fixed location has been widely used. Recently, a mobile relay using a wireless resource as a backhaul and simultaneously functioning as a base station and a relay in a wireless communication system has been actively studied. Such a mobile relay moves autonomously and constitutes a small cell.
In this regard, Korean Patent Laid-open Publication No. 2013-0124197 (entitled “Mobile relay station and handover method thereof”) discloses a handover method of a mobile relay station, including: determining, by a mobile relay station relaying data from a subordinate device to a first base station, whether to perform handover from the first base station to a second base station; when it is determined to perform handover in the determining operation, receiving a first message including first information indicating whether handover is admitted, from the first base station; and when handover admission information is included in the first message, transmitting a second message including a service unavailability section during which a service is not provided to the subordinate device, to the subordinate device.